NOEL KING, HOST:
Scientists from planet Earth will land another mission on Mars today. NASA calls the rover Perseverance.
NPR science correspondent Joe Palca has been following this one. Good morning, Joe.
JOE PALCA, BYLINE: Morning, Noel.
KING: Can we talk about the logistics of this? They have to get a hurtling projectile to land safely on Mars. How is this done?
PALCA: Yeah, what's the big trick? It's going 12,000 mph, and they have to land it at 2 mph - no problem. Well, what happens is the rover is packed up into something called the aeroshell, which hits the top of the atmosphere in Mars. And the atmosphere slows the craft down. And it's friction. It heats up - that's why there's a heat shield - but that does slow it down quite a bit. But then there's a giant parachute that slows it down further. And then finally, there's something called the sky crane, which is a jetpack that flies over the landing site - to the landing site and then lowers the rover down on a tether and then cuts a cord and flies away.
But the interesting thing is this is the same landing system that the last rover used - called Curiosity. But it's been made more up to date by the fact that it's got this smart landing system, so it can actually look for a good place to land. If it doesn't like the first place it picks, it can fly to the next one. But as modern as all the computers and navigation systems are on this new rover, the design of the rocket engines on the sky crane is actually 50 years old.
JOE CASSADY: Believe it or not, those engines all trace their way back to the Viking landers.
PALCA: That's Joe Cassady. He's executive director for space at Aerojet Rocketdyne, the company that makes the rocket engine. The Viking missions landed on Mars in the mid-70s. And Cassady says the rocket design depended on a special valve that made it possible to vary the rocket's thrust.
CASSADY: The funny part is, back in the '70s, we had a supplier that actually developed that for us. When JPL came back to us in the latter part of the first decade of the 21st century and said, we want you to do that again, that supplier was no longer in business.
PALCA: But luckily, they were able to find an alternate supplier who'd make the valve for them.
KING: Very luckily. What is Perseverance looking for on Mars?
PALCA: Well, it's landing in a place called Jezero Crater, which was - they think - a lakebed 3 1/2 - or a lake 3 1/2 billion years ago. And the idea is there might, might, might have been microbes in the lake. So they'll be cameras on the rover that will study the appearance of rocks, looking for things like stromatolites, which are structures left behind by mats of bacteria. There are also instruments on the rover that will measure the chemical and mineral composition of the rocks at the landing site. And Nina Lanza is a geologist at Los Alamos National Lab and a scientist on one of those instruments called SuperCam.
NINA LANZA: See, this is the kind of thing that a geologist needs, right? We need both chemistry - what's in a rock - and mineralogy - how it's arranged.
PALCA: So knowing those things tells a lot about the conditions under which the rock formed and whether or not those conditions were conducive to life.
KING: I ask this excitedly. Could we be getting news soon saying that there was life on Mars?
PALCA: Well, it's one of those news stories where people get very excited. But they will also say, I'm from Missouri; prove - show me. So that's actually the idea of this. They may see things that look like there might have been life there, but they say to confirm that they have to bring the rocks back to Earth. And in fact, that's what this mission is going to do. It's going to collect samples that a future mission will return to Earth.
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KING: OK. NPR Mars correspondent Joe Palca. Thanks, Joe.
PALCA: A new title - that's great. You're welcome.
(SOUNDBITE OF NORTHCAPE'S "STATIC THEME") Transcript provided by NPR, Copyright NPR.
